1. Field of the Invention
The present invention relates to an image capturing apparatus capable of extracting a moving object and picking it up, and a method for adjusting the image capturing apparatus.
2. Description of the Related Art
In an image pickup field, there has been studied the detection of a moving object in order to monitor, for example, an illegal intruder. Conventional moving object detecting technique typically includes an inter-frame difference method (for example, a method for taking a difference between different frames such as a previous screen and a current screen) or a background difference method (for example, a method for taking a difference between a background image and an input image). The inter-frame difference method is disclosed in, for example, Japanese Patent Application Laid-open No. 05-145823, and further, the background difference method is disclosed in, for example, U.S. Pat. No. 5,606,376.
In the meantime, there have been proposed various image capturing apparatuses per se. In particular, with respect to the width of a dynamic range, Japanese Patent Application Laid-open No. 2001-36817, for example, discloses an image capturing apparatus having a wide dynamic range, comprising a solid image pickup element including a photosensitive element for generating an electric signal according to an incident light intensity in a picking-up pixel and a transistor for logarithmic transformation, for converting the incident light intensity to the photosensitive element in a naturally logarithmic manner so as to output it.
In this image capturing apparatus, the transistor for logarithmic transformation includes a control electrode, a first electrode and a second electrode, wherein an output from the photosensitive element is input into the first electrode in the transistor for logarithmic transformation. An image of an object can be picked up by applying a first voltage to the second electrode in the transistor for logarithmic transformation. Thereafter, a second voltage is applied to the second electrode in the transistor for logarithmic transformation, and then, a current greater than that before the application of the second voltage is made to flow in the transistor for logarithmic transformation, so that the transistor is reset.
Here, as for the detection of the moving object, the conventional inter-frame difference method or background difference method requires the complicated processing of a signal from the image pickup element, and therefore, the burden of the signal processing is large in an image pickup system.
In view of the above-described problems observed in the prior art, an object of the present invention is to provide an image capturing apparatus capable of easy detection of the existence of a moving object without requiring any complicated signal processing and capable of moving object extraction image pickup in an image pickup region over a wide luminance range.
Furthermore, another object of the present invention is to provide a method for adjusting such an image capturing apparatus in the mode in which the moving object extraction image pickup can be achieved.